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Iodine Deficiency and Hypothyroidism in Early Pregnancy

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Question

I am an practising endocrinologist in India a relatively Iodine deficienct region. Wide spread availbility of Thyroid funciton testing has brought many patients with mild hypothyroidism in the 1st trimister with TSH of 10 to 15 and a low free T4. What will be the plan of mamagent and if at all termination of preganay is advised.

Dr Sandeep Julka MD DM

Response

I thank you for your relevant questions (see below) and I will try to provide precise answers to you.

  1. Serum TSH values of 10-15 mU/L in the first trimester of pregnancy accompanied by low serum free T4 levels are clear indications of overt (mild to moderate) hypothyroidism. Since you mention that this is frequently observed in your pregnant patients and occurs in an area known to be ‘relatively’ (I guess what you meant is ‘mildly’) iodine-deficient, your information indicates that the wider availability of thyroid function testing allows to reveal an frequent underlying clinical condition, that is hypothyroidism due to iodine deficiency during pregnancy (for further reading, see the review articles by D. Glinoer & F. Delange in Thyroid, volume 10, pages 871-887, 2000, entitled “The potential repercussions of maternal, fetal, and neonatal hypothyroxinemia on the progeny” and by D. Glinoer in Thyroid, volume 11, pages 471-481, 2001, entitled “Pregnancy and Iodine”).
  2. Concerning the ‘plan of management’, you should refer to the recent update on iodine fortification during pregnancy approved by WHO. This important document was published as a special issue in Public Health Nutrition (Volume 10, Number 12(a), December 2007) and can be obtained in your country via your Ministery of Health or the local WHO section, or else the local UNICEF section. The main recommendation is that women should have a daily iodine intake of 200-300 microgr/day during pregnancy. To implement such requirements, different means have been proposed that depend upon the local availability of dietary iodine fortification programmes via iodized salt (but salt consumption is obviously restricted during pregnancy) or supplements of potassium iodide given alone or added to multivitamin pills, for instance. In some areas, it may even be easier to prescribe L-thyroxine individually in order to restore euthyroidism as rapidly as possible, although this proposal is not logical (etiologically) when hypothyroidism results from iodine deficiency.
  3. There is no recommendation to advise ‘termination of pregnancy’ (as far as I know). The main concerns raised by your observations are the health status of both the pregnant woman (because hypothyroidism has detrimental effects on the outcome of pregnancy) and of the future child (because of the known association between maternal thyroid underfunction and the increased risks of impairment of fetal neurological development).
  4. Finally, in your position of ‘practicing endocrinologist’, my suggestion is that you use all means directly available to you to combat maternal hypothyroidism (from its detection by thyroid function testing to its treatment by iodine supplementation or even thyroxine administration). In addition, you should inform your local health authorities of the need to rapidly implement iodine fortification in women who are in the childbearing age and pregnant. For this more political aspect, you should probably contact the Asian representatives in the ICCIDD organization (you can e-mail Michael Zimmermann or Cres Eastman)

Daniel GLINOER, MD